The present invention relates to switch valves used in air-conditioner refrigerant circuits, and more particularly, to switch valves used in refrigerant circuits having hot gas circuits.
A typical automotive air-conditioner refrigerant circuit includes a hot gas circuit. When the air conditioner warms the passenger compartment, heated and pressurized refrigerant gas (hereinafter referred to as xe2x80x9chot gasxe2x80x9d) circulates in the hot-gas circuit. FIG. 5 shows a prior art refrigerant circuit of an automotive air-conditioner. The refrigerant circuit includes a compressor 10, a condenser 11, a receiver 12, a check valve 9, a depressurizing device (expansion valve) 13, an evaporator 14, and an accumulator 15. These constituents are arranged in this order and connected with each other by a pipe 16 to define the refrigerant circuit. The compressor 10 is actuated by an engine (not shown).
A first electromagnetic valve 17 is located in a section of the pipe 16 between the compressor 10 and the condenser 11. A first bypass pipe 20 constitutes a hot gas circuit and has an inlet 20a connected to a section of the pipe 16 between the compressor 10 and the first electromagnetic valve 17. The first bypass pipe 20 also has an outlet 20b connected to a section of the pipe 16 between the depressurizing device 13 and the evaporator 14. Another depressurizing device 22 is provided in the first bypass pipe 20. A second electromagnetic valve 18 is located in the first bypass pipe 20 upstream from the depressurizing device 22.
The depressurizing device 22 depressurizes the hot gas discharged from the compressor 10 to a predetermined value.
The depressurized hot gas is then sent to the evaporator 14.
In this case, it is preferred that the pressure in the first bypass pipe 20 be 1.47 MPa upstream of the depressurizing device 22 and 0.20 to 0.39 MPa downstream of the depressurizing device 22.
A second bypass pipe 40 has an inlet connected to the section of the pipe 16 between the compressor 10 and the first electromagnetic valve 17. The second bypass pipe 40 further has an outlet connected to a section of the pipe 16 between the accumulator 15 and the compressor 10. Another depressurizing device 42 is provided in the second bypass pipe 40. A third electromagnetic valve 41 is provided in the second bypass pipe 40 and located upstream from the depressurizing device 42. The first to third electromagnetic valves 17, 18, 41 are controlled by a controller 100 constituted by, for example, a computer.
When the air conditioner cools the passenger compartment, the controller 100 opens the first electromagnetic valve 17 and closes the second and third electromagnetic valves 18, 41. Refrigerant thus circulates in the pipe 16 without passing through the bypass pipes 20, 40. Specifically, the compressor 10 sends high-pressure gas to the condenser 11. The condenser 11 condenses the gas and sends the gas to the evaporator 14 via the receiver 12, the check valve 9, and the depressurizing device 13. The evaporator 14 cools the ambient air by transferring heat between the ambient air and the condensed refrigerant. The heat transfer evaporates refrigerant, and the evaporated refrigerant gas returns to the compressor via the accumulator 15.
The depressurizing device 13 adjusts the amount of the refrigerant sent by the condenser 11 to the evaporator 14 in accordance with the temperature or pressure at the outlet of the evaporator 14. The accumulator 15 accumulates liquid refrigerant, or refrigerant remaining non-evaporated after passing through the evaporator 14. This structure prevents the liquid refrigerant from returning to the compressor 10.
When the air conditioner warms the passenger compartment, the controller 100 first performs a warm-up procedure for the warming operation. That is, the controller 100 closes the first and second electromagnetic valves 17, 18 and opens the third electromagnetic valve 41. The refrigerant gas from the compressor 10 thus returns to the compressor 10 via the second bypass pipe 40. The depressurizing device 42 in the second bypass pipe 40 increases the pressure of the refrigerant gas exiting the compressor 10 (the discharge pressure of the compressor 10).
When a predetermined time elapses after the controller 100 starts the warming operation, or when the discharge pressure of the compressor 10 reaches a predetermined value, the controller 100 opens the second electromagnetic valve 18 and closes the third electromagnetic valve 41. Accordingly, the air conditioner initiates a normal procedure for the warming operation. That is, the refrigerant gas discharged from the compressor 10, or hot gas, is sent to the evaporator 14 via the first bypass pipe 20. The evaporator 14 warms the ambient air by transferring heat between the ambient air and the hot gas. The refrigerant gas is thus cooled due to the heat transfer and is returned to the compressor 10 through the accumulator 15. In this manner, the refrigerant gas circulates in the hot gas circuit, which is formed by the first bypass pipe 20, when the air conditioner performs the normal warming procedure.
As described, in the prior art refrigerant circuit shown in FIG. 5, three electromagnetic valves 17, 18, 41 are used for switching the refrigerant circuit between the cooling operation and the warming operation. This complicates the circuit configuration and the circuit control procedure, thus raising the manufacturing cost and the power consumption.
It is an objective of the present invention to provide a switch valve simplifying configuration of a refrigerant circuit having a hot gas circuit.
To achieve the above objective, a switch valve according to the present invention comprises a single valve housing. A first passage is formed in the valve housing to permit a fluid to flow into the valve housing. A second passage is formed in the valve housing to permit, at selected times, the fluid in the first passage to exit the valve housing. A third passage is formed in the valve housing to permit, at selected times, the fluid in the first passage to exit the valve housing. A first valve mechanism is incorporated in the valve housing for selectively connecting and disconnecting the first passage with the second passage in accordance with an external instruction. A second valve mechanism is incorporated in the valve housing for selectively connecting and disconnecting the first passage with the third passage in accordance with the difference between the pressure in the first passage and the pressure in the second passage.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.